This invention relates to a system and a process for removing fluidizable solid particulate material from a first zone or vessel, such as a reactor, operating at an elevated temperature and pressure and delivering such solids to a second zone at a reduced temperature and pressure.
There are various systems or processes wherein a reactant in fluidizable solid particulate form is suspended in a reactor by a fluidizing gas. The fluidizing gas can be reactive to the suspended particles and the reaction product removed as a volatile material. Where such processes operate at elevated temperatures such as 500.degree. C. or 600.degree. C. and at some positive pressure, a problem presents itself in removing the unreacted particulate matter from the reactor. One example occurs in the chlorination of alumina to provide aluminum chloride. Such a process is shown in U.S. Pat. No. 3,842,163 wherein a system is shown for reacting fluidized coked alumina particles with chlorine to produce aluminum chloride useful in the production of aluminum. As indicated in U.S. Pat. No. 3,842,163, incorporated herein by reference, the desired character of alumina is the porous condition (such as gamma phase) which is reactive with chlorine as opposed to the low surface area condition (commonly designated the alpha phase) which is relatively unreactive with chlorine in that process. However, it is difficult to avoid at least some alpha alumina in the coked alumina charge, for instance 0.1 to 4.5%, and this alpha alumina is not consumed by reaction, but rather accumulates in the reactor to deplete its reaction zone volume and impede operation in the process according to U.S. Pat. No. 3,842,163. It is the unreacted alpha alumina which needs to be drained or removed to restore the depleted reactor volume. However, draining alpha alumina at 600.degree. to 800.degree. C. presents certain materials handling and safety problems. Accordingly, one practice utilized has been to shut down the chlorinator for sufficient time to facilitate removal of the alpha alumina accumulation after which the chlorinator would be restarted. However, this is an obvious interruption in production which is desirably avoided since the interruption could consume a full day in a large size operation where the reactor could be between 10 and 20 feet in diameter. Fluidized solids handling techniques employing seal pots have also been tried, but the success of such has been limited by practical problems and safety considerations.
Accordingly, it is an object of the present invention to provide a process and system and for removing particles from a reactor, such as a reactor for chlorinating fluidized alumina to provide aluminum chloride, with a minimum interruption in the reaction and with a minimum of safety problems.
Another object is to provide such a system and process employing fluidized particle handling techniques to remove the solids particles from the reactor and discharge the same at reduced temperature and pressure.